A young Canadian woman went on a globetrotting adventure she couldn’t afford to post selfies and help smuggle $21 million worth of cocaine into Australia, but is paying for it now.

Melina Roberge has been jailed after pleading guilty to importing nearly 30 kilograms of the drugs on board a cruise liner which docked in Sydney in August 2016.

The 24-year-old was lured by her “sugar daddy” to become a coke mule in exchange for a free holiday, and blamed her actions on a desire to take photos “in exotic locations and post them on Instagram to receive likes and attention”.

Roberge broke down in tears as she was sentenced to a maximum eight years behind bars in the NSW District Court on Wednesday, with a non-parole period of four years and nine months.

Judge Kate Traill labelled it a sad indictment of the negative impact of social media on young people, who lead a "vacuous existence" seeking likes for self worth.

"She was seduced by lifestyle and the opportunity to post glamorous Instagram photos from around the world," the judge said.

"She wanted to be the envy of others. I doubt she is now."

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Roberge was one of three people arrested in the largest drug seizure on a cruise ship docking in Australia.

The court heard Roberge met her "sugar daddy" in 2015, and they began an intimate relationship while she worked as an escort for him.

The much older man pimped Roberge out on a trip to Morocco in May 2016, where he first coaxed her into the drug plot carried out on the seniors' Sea Princess cruise that stopped in Europe, the United States and South America.

Judge Traill said the then 22-year-old was "there to look pretty", acting as a decoy to the seedy drug business below deck.

The judge said Roberge was motivated by profit as she was promised the ticket worth CAD$22,000, 4000 Euros in spending money and more cash once she returned home.

Roberge had been "groomed" with freebies and expensive dinners by her sugar daddy, whom she won't name over fears for her family's safety in Canada.

One of her accomplices, Isabelle Lagace, 30, was sentenced in November to at least four-and-a-half years in jail after admitting she stashed the cocaine in the pair's cabin to clear a $20,000 debt.

Andre Tamin, in his sixties, has also pleaded guilty and will be sentenced later this year, while a fourth trafficker disembarked the ship before it reached Sydney.

In an affidavit tendered to court, Roberge wrote that at the time she was "a stupid young woman" who was governed by superficiality.

The court heard Roberge had always been preoccupied with her appearance and "her main hobby in prison is training at the gym".

Judge Traill took into account Roberge's guilty plea on the eve of the trial, her prior good character and deep remorse.